Aphid Control, Lemon Thyme and Allergies

I grow and sell herbs, and I have aphids in my greenhouse. What can I do to get rid of them? I ordered ladybugs, but theyre taking forever to clean the parsley. Is there anything I can use on them that is organic, or that won't ruin the herbs to clean the aphids off? Someone told me vinegar and water?

Aphids are getting harder to control. We have noticed that aphids are less susceptible to insecticidal soap than they used to be. Insecticidal soap still kills some aphids, but it doesn't seem to give the complete kill that we remember.
One organic greenhouse grower claims that nitrogen is the root of the problem. He claims that he had has success by simply reducing the nitrogen injected in his water. We have not verified that, and we are reluctant to sacrifice plant quality.
Ladybugs do a good job bringing aphid populations down. You need to be heavy on the application rate; you need to see ladybugs on almost every plant. But ladybugs can't get into every crevice in the plants and always the aphids rebound from those crevices, so ladybugs must be seen as a temporary control until you move the plants out of the greenhouses.
Lacewings are another beneficial insect that you can try.
Although it is not considered organic by certifiers, nicotine is an excellent control of aphids. In the smoke bomb form it is relatively harmless as far as residues on plants go.

Also, I have a customer who purchased lemon thyme, but he's allergic to all citrus. Will he be allergic to the lemon thyme also?

With allergies it is always a hazardous business to predict someone's reaction, but I would think that lemon thyme will not provoke the same reaction that citrus fruits do. It depends on what components in the citrus fruit are causing the reaction, and it seems to me that the chances are high that whatever it is, it is not in lemon thyme. Lemon thyme's essential oil is different from that in the lemon citrus.
Probably the only sensible thing you can tell your customer is to try a small exposure to lemon thyme (touch leaves, drink tea, etc.) unless the customer's reaction to citrus is life-threatening, in which case he or she should avoid lemon thyme altogether.